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Sulfated seaweed polysaccharides as multifunctional materials in drug delivery applications

Publication . Cunha, Ludmylla; Grenha, Ana

In the last decades, the discovery of metabolites from marine resources showing biological activity has increased significantly. Among marine resources, seaweed is a valuable source of structurally diverse bioactive compounds. The cell walls of marine algae are rich in sulfated polysaccharides, including carrageenan in red algae, ulvan in green algae and fucoidan in brown algae. Sulfated polysaccharides have been increasingly studied over the years in the pharmaceutical field, given their potential usefulness in applications such as the design of drug delivery systems. The purpose of this review is to discuss potential applications of these polymers in drug delivery systems, with a focus on carrageenan, ulvan and fucoidan. General information regarding structure, extraction process and physicochemical properties is presented, along with a brief reference to reported biological activities. For each material, specific applications under the scope of drug delivery are described, addressing in privileged manner particulate carriers, as well as hydrogels and beads. A final section approaches the application of sulfated polysaccharides in targeted drug delivery, focusing with particular interest the capacity for macrophage targeting.

2016-07Journal article

Open Access

A thyroid hormone regulated asymmetric responsive centre is correlated with eye migration during flatfish metamorphosis

Publication . Campinho, Marco António; Silva, Nádia; Martins, Gabriel G.; Anjos, Liliana; Florindo, Claudia; Roman-Padilla, Javier; Garcia-Cegarra, Ana; Louro, Bruno; Manchado, Manuel; Power, Deborah

Flatfish metamorphosis is a unique post-embryonic developmental event in which thyroid hormones (THs) drive the development of symmetric pelagic larva into asymmetric benthic juveniles. One of the eyes migrates to join the other eye on the opposite side of the head. Developmental mechanisms at the basis of the acquisition of flatfish anatomical asymmetry remain an open question. Here we demonstrate that an TH responsive asymmetric centre, determined by deiodinase 2 expression, ventrally juxtaposed to the migrating eye in sole (Solea senegalensis) correlates with asymmetric cranial ossification that in turn drives eye migration. Besides skin pigmentation that is asymmetric between dorsal and ventral sides, only the most anterior head region delimited by the eyes becomes asymmetric whereas the remainder of the head and organs therein stay symmetric. Sub-ocular ossification is common to all flatfish analysed to date, so we propose that this newly discovered mechanism is universal and is associated with eye migration in all flatfish.

2018-08Journal article

Open Access

Estudo da floração e polinização do abacateiro, no Algarve

Publication . Lopes, Maria do Rosário Capela; Duarte, Amílcar

O abacateiro possui características únicas a nível da floração. Apesar das flores serem hermafroditas, apresentam um mecanismo sequencial das suas funções reprodutivas, primeiro abrem como femininas e depois, numa segunda abertura, são funcionalmente masculinas, dificultando a autopolinização. Este mecanismo denomina-se sincronia dicogâmica protogínica. Dependendo do momento do dia em que isso ocorre, os abacateiros são classificados em dois grupos, grupo A e grupo B, que quando colocados em conjunto no mesmo pomar, permitem a polinização entre si. As condições meteorológicas, nomeadamente a temperatura, humidade relativa e nebulosidade modificam o comportamento de ambos os grupos, principalmente, hora de início e duração de cada uma das fases da flor. Uma vez que a maior parte dos estudos sobre floração e polinização em abacateiro têm sido conduzidos em zonas com características edafoclimáticas diferentes das do Algarve, é necessário estudar estes processos, com vista a desenvolver conhecimento e técnicas culturais que permitam aumentar a produtividade dos pomares. Considerando que a cultivar 'Hass' (grupo A) é a mais valorizada comercialmente, aparecendo como cultivar principal em quase todos os pomares portugueses, com polinizadoras do grupo B, foi definida como objetivo avaliar a pertinência da instalação de árvores polinizadoras e a compatibilidade entre 'Hass' e 'Ettinger', 'Bacon' e 'Zutano'. Assim, avaliou-se o seu comportamento floral, através da observação ao longo do dia, durante vários dias, registando o número de flores abertas e seus estágios fenológicos. Os resultados obtidos mostram que a abertura das flores da cultivar ‘Hass’ na fase feminina se concentra principalmente entre as 11 e as 14 horas, podendo apresentar sobreposição com a fase masculina da mesma cultivar. Verificou-se que nos dias mais frios a abertura das flores era mais tardia e permaneciam abertas durante mais tempo. Nas cultivares polinizadoras a abertura das flores na fase masculina é variável, sendo a cultivar ‘Bacon’ a que apresenta uma maior sobreposição com a ‘Hass’ ao longo do dia. Verificouse também que há uma forte correlação entre a produção do ano anterior e o estado fenológico no início dos lançamentos reprodutivos, havendo um claro atraso nas árvores cuja produção foi mais elevada.

2020-07-20Master thesis

Open Access

Eye-movements in implicit artificial grammar learning

Publication . Silva, Susana; Inácio, Filomena; Folia, Vasiliki; Petersson, Karl Magnus

Artificial grammar learning (AGL) has been probed with forced-choice behavioral tests (active tests). Recent attempts to probe the outcomes of learning (implicitly acquired knowledge) with eye-movement responses (passive tests) have shown null results. However, these latter studies have not tested for sensitivity effects, for example, increased eye movements on a printed violation. In this study, we tested for sensitivity effects in AGL tests with (Experiment 1) and without (Experiment 2) concurrent active tests (preference- and grammaticality classification) in an eye-tracking experiment. Eye movements discriminated between sequence types in passive tests and more so in active tests. The eye-movement profile did not differ between preference and grammaticality classification, and it resembled sensitivity effects commonly observed in natural syntax processing. Our findings show that the outcomes of implicit structured sequence learning can be characterized in eye tracking. More specifically, whole trial measures (dwell time, number of fixations) showed robust AGL effects, whereas first-pass measures (first-fixation duration) did not. Furthermore, our findings strengthen the link between artificial and natural syntax processing, and they shed light on the factors that determine performance differences in preference and grammaticality classification tests.

2017-09Journal article

Open Access

Behavioral inhibition in childhood: European Portuguese adaptation of an observational measure (Lab-TAB)

Publication . Faisca, Luis; Ferreira, Laura Inês; Fernandes, Catarina; Gagne, Jeffrey R.; Martins, Ana T.

The assessment of behaviorally inhibited children is typically based on parent or teacher reports, but this approach has received criticisms, mainly for being prone to bias. Several researchers proposed the additional use of observational methods because they provide a direct and more objective description of the child's functioning in different contexts. The lack of a laboratory assessment of temperament for Portuguese children justifies the adaptation of some episodes of the Laboratory Temperament Assessment Battery (Lab-TAB) as an observational measure for behavioral inhibition. Method: In our study, we included 124 children aged between 3 and 9 years and their parents. The evaluation of child behavioral inhibition was made by parent report (Behavioral Inhibition Questionnaire) and through Lab-TAB episodes. Parental variables with potential influence on parents’ reports were also collected using the Social Interaction and Performance Anxiety and Avoidance Scale (SIPAAS) and the Parental Overprotection Measure (POM). Results and Discussion: The psychometric analyses provided evidence that Lab-TAB is a reliable instrument and can be incorporated in a multi-method approach to assess behavioral inhibition in studies involving Portuguese-speaking children. Moderate convergence between observational and parent report measures of behavioral inhibition was obtained. Mothers’ characteristics, as well as child age, seem to significantly affect differences between measures, being potential sources of bias in the assessment of child temperament.

2021-02-21Journal article

Open Access